Issue 5013 - Make parameter const ref when applicable.

src/Utils.cpp

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2017 eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 #include <sstream>
 #include <stdexcept>
 
 #ifdef _WIN32
 #include <Windows.h>
 #include <Shlwapi.h>
 #endif
 
 #include "Utils.h"
 
 using namespace AdblockPlus;
 
-std::string Utils::Slurp(std::istream& stream)
+std::string Utils::Slurp(const std::istream& stream)
 {
   std::stringstream content;
   content << stream.rdbuf();
   return content.str();
 }
 
-std::string Utils::FromV8String(v8::Handle<v8::Value> value)
+std::string Utils::FromV8String(const v8::Handle<v8::Value>& value)
 {
   v8::String::Utf8Value stringValue(value);
   if (stringValue.length())
     return std::string(*stringValue, stringValue.length());
   else
     return std::string();
 }
 
 v8::Local<v8::String> Utils::ToV8String(v8::Isolate* isolate, const std::string& str)
 {
@@ skipping 49 matching lines @@
     if (FAILED(hr))
     {
       throw std::runtime_error("CanonizeUrl failed\n");
     }
   }
   return canonizedUrl;
 
 }
 #endif